Updated schema

+Updated trails table to include URL column
+Added a tentative POI table. May need a POI "type" for icons
+Fixed a spelling error

I noticed that the 15th decimal place is lost during python's float() conversion. This level of precision is higher than a micron and is probably not accurate anyways. We only need to concern ourselves with the 5th most significant decimals as we are limited by smartphone GPS hardware precision.